VBUS power switch

ABSTRACT

This document discusses, among other things, an electronic circuit and method for defaulting to a valid battery supply to power an electronic device. In an example, an electronic circuit can be configured to receive information about the battery supply (e.g., an internal battery), such as the battery supply voltage (V BAT ), and to determine if the battery supply is valid or invalid using the received information (e.g., comparing the V BAT  to a threshold). If V BAT  is valid, the electronic device can default to receiving power from the battery supply. If V BAT  is invalid, the electronic device can receive power from another power supply, such as an external supply.

CLAIM OF PRIORITY

This application claims the benefit of priority under 35 U.S.C. §119(e)of Siulinski et al., U.S. Provisional Patent Application Ser. No.61/348,484, entitled “VBUS POWER SWITCH,” filed on May 26, 2010, theentirety of which is incorporated by reference herein.

BACKGROUND

Many electronic devices can be powered by more than one power supply,such as an internal battery and an external supply, such as a cordedsupply. Typically, when a battery supply and a corded supply are bothvalid and present, the corded supply is chosen to power the electronicdevice. In other examples, a determination can be made between themultiple supplies using one or more characteristics of the supply.

OVERVIEW

This document discusses, among other things, an electronic circuit andmethod for defaulting to a valid battery supply to power an electronicdevice. In an example, an electronic circuit can be configured toreceive information about the battery supply (e.g., an internalbattery), such as the battery supply voltage (V_(BAT)), and to determineif the battery supply is valid or invalid using the received information(e.g., comparing the V_(BAT) to a threshold). If V_(BAT) is valid, theelectronic device can default to receiving power from the batterysupply. If V_(BAT) is invalid, the electronic device can receive powerfrom another power supply, such as an external supply.

In other examples, the electronic circuit and method can include a powersupply override (PSO) option configured to change the defaultconfiguration, for example, to default to the external supply instead ofthe battery supply.

This overview is intended to provide an overview of subject matter ofthe present patent application. It is not intended to provide anexclusive or exhaustive explanation of the invention. The detaileddescription is included to provide further information about the presentpatent application.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIGS. 1-3 illustrate generally example switch circuits.

FIG. 4 illustrates generally an example of a relationship between abattery supply voltage, (V_(BAT)), an external supply voltage (V_(BUS)),a power supply override (PSO) signal, and an internal device voltage(V_(DD)).

DETAILED DESCRIPTION

The present inventors have recognized, among other things, that incertain examples, it can be desirable to default to providing power toan electronic device using a valid battery supply instead of an externalsupply. In certain examples, the battery supply can be more stable orpredictable, gradually falling off from a steady level, or having lessabrupt changes in available power. In an example, an electronic circuit,such as a switch (e.g., a power switch), can be configured to receivepower from both a battery supply and an external supply (e.g., a cordedsupply), to determine if the battery supply is valid or invalid (e.g.,comparing a battery supply voltage (V_(BAT)) to a threshold), anddefault to providing an internal device voltage (V_(DD)) using powerfrom the battery supply if the battery supply is valid. In an example,the electronic circuit can be configured to provide V_(DD) using powerfrom the external supply when the battery supply is present but invalid,or when the battery supply is not present.

In an example, the electronic circuit can automatically transition fromproviding V_(DD) using the battery supply to providing V_(DD) using theexternal supply, or vice versa, without interruption. In certainexamples, V_(DD) can be provided without interruption using the batterysupply, the external supply, or a combination or series of the batterysupply and the external supply. The present inventors have recognized,among other things, that the systems and methods disclosed herein can beimplemented with little or no software changes or modifications toexisting devices, allowing simple adoption for all customers.

In an example, the electronic circuit can be configured to receive powerfrom a plurality of different power supplies, including a battery supplyand one or more external supplies (e.g., a wall charger, an AC-to-DCconverter, a USB bus voltage, or one or more other supplies). In anexample, when the battery supply is not present or invalid (e.g., whenV_(BAT) is below a threshold) and the external supply is present, theelectronic device can be configured to provide power to the electronicdevice using the external supply. When the battery supply is present andvalid (e.g., when V_(BAT) is above a threshold), the electronic circuitcan automatically switch to providing power to the electronic deviceusing the battery supply, even if the battery supply is at a lowervoltage than the external supply.

In an example, the electronic circuit can include a power supplyoverride feature configured to change the default supply, for example,from the battery supply to the external supply. In an example, the PSOcan be user controlled or programmable. For example, if desired, the PSOcan be used to force the electronic circuit to provide power to theelectronic device using the external voltage when the battery voltage ispresent and valid.

In an example, the electronic circuit can be configured to allow theelectronic device (e.g., a portable or mobile device, such as acommunication device, a computing device, a media player, etc.) to bepowered from the external supply under certain conditions where there isno internal battery or control functionality from a processor (e.g.,during production test/setup where the system has not yet beenprogrammed, etc.). In an example, once the electronic device has beenprogrammed and normal battery power has been initialized or restored,the electronic circuit can automatically change to using the batterysupply.

FIG. 1 illustrates generally an example of a system 100 including aswitch 105 configured to receive power from a battery supply, to receivepower from an external supply, to determine if the battery supply isvalid or invalid (e.g., comparing a battery supply voltage (V_(BAT)) toa threshold), and default to providing an internal device voltage(V_(DD)) using power from the battery supply if the battery supply isvalid. In an example, if the battery supply is valid, then only thebattery supply is used to provide V_(DD). In other examples, if thebattery supply is valid, then the external supply is not used to provideV_(DD).

In an example, the switch 105 can be configured to provide V_(DD) usingpower from the external supply (e.g., an external supply voltage, suchas a USB bus voltage, V_(BUS)), and not the battery supply, when thebattery supply is present but invalid, or when the battery supply is notpresent.

In certain examples, the switch 105 can be included as a component of adevice (e.g., a USB switch, a USB transceiver, etc.), or can be coupledto a device configured to receive power from more than one supply (e.g.,a battery supply and an external supply, such as an AC-to-DC converter,a USB bus voltage, etc.). In an example, one or more condition can existdefining when one or more of the first or second voltages are used toprovide the output voltage.

FIG. 2 illustrates generally an example of a system 200 including aswitch 105 and a power supply override (PSO) option including first andsecond switches 110, 111 and an inverter 110. In an example, the switch105 can be configured to receive V_(BAT) from a battery supply, toreceive V_(USB) from an external supply, and to provide an internaldevice voltage (V_(DD)). The switch 105 can include first and secondtransistors 145, 150, and V_(DD) can be provided using at least one ofthe first transistor 145 and V_(BAT) or the second transistor 150 andV_(BUS).

In an example, under normal operation the switch 105 can default toproviding V_(DD) using V_(BAT) when V_(BAT) is present, or when V_(BAT)is present and above a threshold (e.g., a level sufficient to create aninternal device voltage, such as 2.4V, etc.), and using V_(USB) when theV_(BAT) is not present, or when V_(BAT) is present but below thethreshold.

In an example, that a PSO can be configured to override one or moreconditions with respect to V_(BUS) and V_(BAT), e.g., manually oraccording to one or more conditions. For example, if the PSO option isselected, such as by a user, the first and second switches 110, 111 canchange states, and the switch 105 can then default to providing V_(DD)using V_(BUS) when V_(USB) is present, when V_(USB) is present and abovea threshold, or when V_(BUS) is present and greater than V_(BAT), andusing V_(BAT) when V_(BUS) is not present, when V_(BUS) is present butbelow the threshold, or when V_(BUS) is present but less than V_(BAT).

FIG. 3 illustrates generally an example of a system 300 including acomparator 115, a logic gate 120, and a switched power supply 155. In anexample, the comparator 115 can be configured to determine if V_(BAT) isvalid, such as by comparing V_(BAT) to a reference (e.g., a threshold,such as 2.4V, etc.). In the example of FIG. 3, the logic gate 120 caninclude a NOR gate configured to receive the output from the comparator115 and an active low power supply override (PSO) signal.

In certain examples, the system 300 can include glitch eliminationcircuit configured to eliminate temporary glitches arising frommomentary, but not permanent state changes in the system 300. In anexample, the glitch elimination circuit can include a delay circuit 125,an inverter 130, and a logic gate 135. In an example, the glitchelimination circuit can be configured to receive the output from thelogic gate 120 and remove temporary state changes within said output.The amount of delay introduced by the delay circuit 125 can change thelength of the glitch eliminated by the glitch elimination circuit.

In an example, the system 300 can include a break before make circuit140 configured to ensure that V_(BAT), or a battery supply, and V_(BUS),or an external supply, are not inadvertently connected to each other,such as during switching.

In an example, the switched power supply 155 can include first, second,third, and fourth switching transistors 146, 147, 151, 152, the firstand second switching transistors 146, 147 configured to provide aninternal device voltage (V_(DD)) using V_(BAT), and the third and fourthswitching transistors 151, 152 configured to provide V_(DD) usingV_(BUS). In an example, the first, second, third, and fourth switchingtransistors can include p-type metal oxide semiconductor field effecttransistors (MOSFETs). In other examples, the switched power supply 155can include one or more other types or combinations of transistors.

In an example, the break before make circuit 140 can be configured toreceive the determination that V_(BAT) is valid and provide one or moreenable signals to the switched power supply 155. The switched powersupply 155 can provide V_(DD) using at least one of V_(BAT) or V_(BUS),depending on the one or more enable signals.

FIG. 4 illustrates generally an example of a relationship 400 between abattery supply voltage (V_(BAT)), an external supply voltage (V_(BUS)),a power supply override (PSO) signal, and an internal device voltage(V_(DD)), such as according to the example illustrated in system 300 ofFIG. 3. In other examples, one or more other relationships can beobtained, depending on variance in the example circuits disclosed above.

Additional Notes and Examples

In Example 1, a system can include a switch circuit configured toreceive a battery supply voltage, to receive an external supply voltage,and to provide an internal device voltage, the switch circuit includinga comparator configured to determine if the battery supply voltage isvalid, wherein the switch circuit is configured to default to providingthe internal device voltage using the battery supply voltage if thebattery supply voltage is valid.

In Example 2, the switch circuit of Example 1 is optionally configuredto receive information from the comparator and to provide the internaldevice voltage using the battery supply voltage when the informationfrom the comparator indicates that the battery supply voltage is abovethe reference.

In Example 3, a system can include a switch circuit configured toreceive a battery supply voltage, to receive an external supply voltage,and to provide an internal device voltage, the switch circuit includinga comparator configured to determine if the battery supply voltage isvalid and a power supply override circuit configured to receiveinformation about a supply voltage selection, wherein the switch circuitis configured to default to providing the internal device voltage usingthe battery supply voltage if the battery supply voltage is valid andthe information about the supply preference indicates that the batterysupply voltage is selected, and wherein the switch circuit is configuredto default to providing the internal device voltage using the externalsupply voltage if the information about the supply preference indicatesthat the external supply voltage is selected.

In Example 4, the switch circuit of any one or more of Examples 1-3 isoptionally configured to provide the internal device voltage using theexternal supply voltage if the battery supply voltage is invalid.

In Example 5, the comparator of any one or more of Examples 1-4 isoptionally configured to receive the battery supply voltage and tocompare the battery supply voltage to a reference.

In Example 6, the switch circuit of any one or more of Examples 1-5 isoptionally configured to receive information from the comparator and toprovide the internal device voltage using the battery supply voltagewhen the information from the comparator indicates that the batterysupply voltage is above the reference.

In Example 7, the switch circuit of any one or more of Examples 1-6 isoptionally configured to receive information from the comparator and toprovide the internal device voltage using the battery supply voltagewhen the information from the comparator indicates that the batterysupply voltage is above the reference and the information about thesupply preference indicates that the battery supply voltage is selected.

In Example 8, any one or more of Examples 1-7 optionally includes amobile device configured to be coupled to an internal battery and anexternal supply, wherein the battery supply voltage includes voltagefrom the internal battery, wherein the external supply voltage includesvoltage from the external supply, and wherein the internal devicevoltage is configured to power the mobile device.

In Example 9, the external supply of any one or more of Examples 1-8optionally includes a universal serial bus (USB) supply configured to becoupled to the mobile device using a USB port.

In Example 10, a method can include receiving a battery supply voltage,receiving an external supply voltage, determining if the battery supplyvoltage is valid, and providing, by default, an internal device voltageusing the battery supply voltage if the battery supply voltage is valid.

In Example 11, the determining if the battery supply voltage is valid ofany one or more of Examples 1-10 optionally includes comparing thebattery supply voltage to a reference.

In Example 12, the providing the internal device voltage using thebattery supply voltage of any one or more of Examples 1-11 optionallyincludes when the information from the comparator indicates that thebattery supply voltage is above the reference.

In Example 13, a method can include receiving a battery supply voltage,receiving an external supply voltage, determining if the battery supplyvoltage is valid, receiving information about a supply voltageselection, providing an internal device voltage using the battery supplyvoltage if the battery supply voltage is valid and the information aboutthe supply preference indicates that the battery supply voltage isselected, and providing the internal device voltage using the externalsupply voltage if the information about the supply preference indicatesthat the external supply voltage is selected.

In Example 14, any one or more of Examples 1-13 can optionally providethe internal device voltage using the external supply voltage if thebattery supply voltage is invalid.

In Example 15, the determining if the battery supply voltage is valid ofany one or more of Examples 1-14 optionally includes comparing thebattery supply voltage to a reference, wherein the providing theinternal device voltage using the battery supply voltage includes whenthe information from the comparator indicates that the battery supplyvoltage is above the reference.

In Example 20, the receiving the battery supply voltage of any one ormore of Examples 1-19 optionally includes from an internal battery of amobile device, the receiving the external supply voltage of any one ormore of Examples 1-19 optionally includes from an external supply of themobile device, and any one or more of Examples 1-19 optionally includespowering at least a portion of the mobile device using the internaldevice voltage.

In Example 21, a system or apparatus can include, or can optionally becombined with any portion or combination of any portions of any one ormore of Examples 1-20 to include, means for performing any one or moreof the functions of Examples 1-20, or a machine-readable mediumincluding instructions that, when performed by a machine, cause themachine to perform any one or more of the functions of Examples 1-20.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” All publications, patents, and patent documentsreferred to in this document are incorporated by reference herein intheir entirety, as though individually incorporated by reference. In theevent of inconsistent usages between this document and those documentsso incorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to impose numerical requirements on their objects.

The above description is intended to be illustrative, and notrestrictive. For example, although the examples above have beendescribed relating to p-type devices, one or more examples can beapplicable to n-type devices. In other examples, the above-describedexamples (or one or more aspects thereof) may be used in combinationwith each other. Other embodiments can be used, such as by one ofordinary skill in the art upon reviewing the above description. TheAbstract is provided to comply with 37 C.F.R. §1.72(b), to allow thereader to quickly ascertain the nature of the technical disclosure. Itis submitted with the understanding that it will not be used tointerpret or limit the scope or meaning of the claims. Also, in theabove Detailed Description, various features may be grouped together tostreamline the disclosure. This should not be interpreted as intendingthat an unclaimed disclosed feature is essential to any claim. Rather,inventive subject matter may lie in less than all features of aparticular disclosed embodiment. Thus, the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separate embodiment. The scope of the invention should bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A system, comprising: a USB switch circuitconfigured to receive a battery supply voltage, to receive a USB busvoltage, and to provide an internal device voltage for the USB switchcircuit, the USB switch circuit including: a comparator configured todetermine if the battery supply voltage is valid; and a power supplyoverride circuit configured to receive an override selection; andwherein, in normal operation, when the power supply override circuitdoes not receive the override selection, the USB switch circuit isconfigured to provide the internal device voltage using only the batterysupply voltage if the battery supply voltage is valid and the USB busvoltage is valid, and using only the USB bus voltage if the batterysupply voltage is invalid; and wherein, in override operation, when thepower supply override circuit receives the override selection, the USBswitch circuit is configured to provide the internal device voltageusing only the USB bus voltage if the USB bus voltage is valid.
 2. Thesystem of claim 1, wherein the comparator is configured to compare thebattery supply voltage to a reference.
 3. The system of claim 2,wherein, in normal operation, when the power supply override circuitdoes not receive the override selection, the USB switch circuit isconfigured to receive information from the comparator and to provide theinternal device voltage using the battery supply voltage when theinformation from the comparator indicates that the battery supplyvoltage is above the reference.
 4. The system of claim 1, wherein thesystem includes a mobile device configured to be coupled to an internalbattery, wherein the battery supply voltage includes voltage from theinternal battery, wherein the USB bus voltage includes voltage from anAC-to-DC converter coupled to a USB port of the mobile device.
 5. Thesystem of claim 1, wherein, in override operation, when the power supplyoverride circuit receives the override selection, the switch circuit isconfigured to provide the internal device voltage using only the batterysupply voltage if the USB bus voltage is invalid.
 6. A method,comprising: receiving a battery supply voltage at a first input of a USBswitch circuit; receiving a USB bus voltage at a second input of the USBswitch circuit; determining if the battery supply voltage is valid; andreceiving information about a supply override selection; providing, innormal operation, when a supply override selection has not beenreceived, an internal device voltage for the USB switch circuit usingonly the battery supply voltage if the battery supply voltage is validand the USB bus voltage is valid, and using only the USB bus voltage ifthe battery supply voltage is invalid; and providing, in overrideoperation, when a supply override selection has been received, theinternal device voltage for the USB switch circuit using only the USBbus voltage if the USB bus voltage is valid.
 7. The method of claim 6,wherein the determining if the battery supply voltage is valid includescomparing the battery supply voltage to a reference.
 8. The method ofclaim 7, wherein the providing the internal device voltage using thebattery supply voltage includes when the information from the comparatorindicates that the battery supply voltage is above the reference.
 9. Themethod of claim 6, wherein the receiving the battery supply voltageincludes from an internal battery of a mobile device; and wherein thereceiving the USB bus voltage includes from an AC-to-DC convertercoupled to a USB port of the mobile device.
 10. The method of claim 6,including: providing, in override operation, when the supply overrideselection has been received, the internal device voltage for the USBswitch circuit using only the battery supply voltage if the USB busvoltage is invalid.